1. Field of the Invention
The present invention relates to an apparatus and method for landscape edging, and more particularly to a mowing and retaining strip which can be used for edging beds of landscape fill and for preventing the growth of vegetation under and adjacent to fencing.
2. Summary of the Related Art
Landscape edgings and fence guards heretofore proposed generally consist of a retaining strip, a mowing strip, or both. Retaining strips (RS) are elongated barriers installed longitudinally along the surface of the ground such that the barrier is substantially perpendicular to the ground. In landscape edgings, RS are used either to separate different types of landscaping materials (such as lawn, gravel walkways, beds of decorative rock, beds of bark, gardens etc.) or to retain elevated beds of earth or other landscaping fill. In fence guards, RS are abutted along the base of a fence and are used to maintain a desired spatial relationship between a mowing strip and the fence and thus protect the bottom edge of the fence from damage by a lawnmower, a lawn edging device, or animals; to protect lawnmowers, lawn edging devices, and animals from damage by the bottom edge of the fence; and to discourage animals from digging underneath fences.
Mowing strips (MS) are installed along a lawn border and have a top face that is flush with the surface of the ground. By running the wheels attached to one side of a lawnmower onto and along a MS, one can cut all grass immediately adjacent to the MS. Consequently, MS are used to reduce or eliminate the need for horizontal trimming of grass at lawn borders.
Most MS currently in use are constructed by end to end assemblage of rigid segments formed from concrete, wood, or brick. Such MS must be buried into the ground so that the top surface of the strip is essentially at ground level. Such subterranean installation is tedious, requiring the digging of trenches, and, in the case of concrete MS, construction of forms. Due to their thickness, none of these MS are as easily installed under existing fence as in open, unobstructed terrain. Concrete or mortared brick MS are very difficult to remove, and cannot be conveniently reused in a different location. Unmortared bricks and unstaked wood occassionally get knocked out of position. Wood MS suffer the additional disadvantages of rotting and of not conforming easily to changes in ground slope.
MS can be classified as being of the continuous elongated type or of the segmented type. The segmented type comprises a plurality of relatively short sections (segments) installed in series. Because the sections composing segmented MS are relatively short (typically less than 4 feet) in length, a relatively large number of sections is needed to construct a given length of MS, and the resulting MS will have a relatively large number of joints between sections. One of the problems with segmented MS is that their construction can be tedious and time-consuming, requiring the assembly of a relatively large number of pieces. An even more serious problem with segmented MS is maintenance of the joints between sections. If no deliberate attempt is made to connect adjacent abutted sections of a segmented MS, grass can easily encroach across the MS barrier between the abutted sections, and also, the sections can easily be knocked out of alignment.
Examples of segmented MS that demonstrate these problems are those constructed of concrete blocks. Furthermore, virtually all deliberate attempts to overcome these problems by connecting or overlapping adjacent MS sections are defeated by the natural expansion and contraction of the ground that accompanies freeze/thaw cycles, changes in ground moisture content, fire ant activity, or the like. For example, such expansion and contraction of the ground often cracks the joints of mortared brick MS. Thus it is very desirable to minimize the number of joints in a MS.
Poured concrete MS, although not of the segmented type, also are often cracked by the natural expansion and contraction of the ground.
A continuous elongated MS differs from a segmented MS in that, within the limits of practical manufacture, transportation, and storage, the entire length of a continuous elongated MS is provided by a single, integral, continuous strip. Another distinction between continuous elongated MS and segmented MS is that continuous elongated MS are typically manufactured in lengths exceeding 4 feet and are intended to be cut to the desired length by the installer. In contrast, few if any of the sections of a segmented MS are altered in length by the installer.
U.S. Pat. Nos. 3,384,351 and 4,381,822 describe continuous elongated flexible thin plastic MS that are staked onto the top of the ground adjacent or under a fence. Such MS avoid all of the disadvantages just described for concrete, wood, or segmented MS, but cannot function as retainer strips (RS) for landscaped beds.
Landscaping sheet is often used to prevent growth of weeds or grass in flower beds, bush beds, or areas covered with landscape fill. The edges of landscaping sheet must be secured to prevent them from being shredded by a lawnmower or from being overrun with weeds and grass. In this patent application, the term "landscaping sheet" includes geotextile; plastic mulch; landscape, landscaping, or earth fabric, film, sheet, blanket or mat; and the like. In this patent application, the term "landscape fill" includes sand, bark, mulch, or hard surface means such as concrete, asphalt, mortared brick, loose brick, paving stones, rock, gravel, and the like.
If the edges of landscaping sheet are secured by partially buried MS, several problems result. One is that the landscaping sheet edges tend to loosen and pull up as the surrounding ground expands and contracts with freeze/thaw cycles, changes in ground moisture content, fire ant activity, or the like. Another is that dirt and debris can wedge between the landscaping sheet and the MS, providing gaps through which weeds will grow. Still another problem is that landscaping sheet tends to be stressed and torn at the points where it is bent and buried next to a partially buried MS. The frequency at which landscaping sheet must be maintained or replaced entirely greatly exceeds the usual and expected life of MS. The required maintenance or replacement of landscaping sheet usually necessitates removal and reinstallation of the MS, which, for partially buried MS, is relatively difficult. Removal and reinstallation of MS also would be required to service drip irrigation tubing and outlets placed underneath landscaping sheet with edges secured by MS.
Thin plastic RS secured to the ground by a substantial buried component are disclosed in U.S. Pat. Nos. 3,387,786, 3,788,001, and 4,281,473. The buried component provides two functions: it supports the above-ground component and it restricts grass from growing underneath the strip into an area where grass is not wanted. However, as with concrete, wood, or brick MS, installation of the buried component is tedious, requiring the digging of trenches. Also for the same reasons as with concrete, wood, or brick MS, use of RS with buried components to secure the edges of landscaping sheet is not practical. Although thin plastic retaining strips bend easily in the horizontal plane perpendicular to their axis of height, such strips lack the vertical flexibility needed to conform to changes in ground slope while maintaining a perpendicular relationship between the ground surface and the retaining strip barrier.
Relatively thin plastic RS with buried components all have the serious problem of tending to pull up out of the ground, permitting grass to encroach underneath the strip. To reduce this tendency, several means have been used individually or in combination, including horizontal ribbing or corrugation, stakes that are driven diagonally through the underground portion before it is buried, stakes that clip over the top edge of the strip and that are driven into the ground immediately next to the strip, and upwardly angled flanges attached to the buried portion of the RS. However, none of these means adequately reduces the tendency of thin plastic RS to pull up out of the ground, particularly when the ground is subject to heaving by freezing or changes in moisture content.
Relatively thick RS installed on the top of the ground, such as landscaping timbers or the RS described in U.S. Pat. No. 1,916,494 are not sufficiently flexible to conform easily to changes in ground slope. Such inflexibility usually necessitates a vertically angled joint in the RS to accommodate a significant change in ground slope. Even when such joints are used, the inability of a RS to conform to changes in ground slope will result in occassional gaps between the ground and the RS. Grass can encroach underneath the RS through such gaps. When thick RS installed on the top of the ground are used to secure the edges of landscaping sheet on a ground surface of changing slope, occassional gaps will occur between the landscaping sheet and the RS. The gaps between the landscaping sheet and the RS will permit grass to encroach underneath the RS through the gaps into an area where grass is not wanted.
Lawn edging strips involving the combination of a mowing strip and a retainer strip have been proposed. The MS/RS combinations disclosed in U.S. Pat. Nos. 2,184,904, 2,713,751, 3,515,373, 3,495,352, 3,545,127, and 4,372,079 all have a substantial portion of their RS buried underground. Furthermore, the MS and the RS of these combinations often are not integrally connected. Such combinations have the following disadvantages.
The presence of the underground RS component precludes use of the MS to secure landscaping sheet.
Installation of the underground RS components almost always requires the labor-intensive digging of trenches. Even when the RS are, in principle, thin enough to be driven into the ground with a hammer, this method of installation is usually less effective than that of digging a trench, placing the RS inside the trench, and packing soil firmly against both sides of the RS. In the case of a thin continuous elongated RS, one end can be hammered into the ground only a very short distance before the rest of the RS must be driven into the ground by a nearly equivalent distance. However, hammering on one end of the RS tends to pull the other end of the RS out of the ground. The iterative nature of such installation results in the ground being pushed away from the walls of the RS, preventing a tight fit of the RS into the ground and leaving the RS poorly secured.
Thin retaining strips, whether hammered or buried into the ground, all have the serious problem of tending to be pulled up out of the ground by the natural expansion and contraction of the ground caused by freeze/thaw cycles, changes in ground moisture content, fire ant activity, or the like. Special means are usually employed for alleviating this problem, particularly upwardly angled flanges attached in a lengthwise parallel fashion to the underground portion of the RS. However, such flanges significantly increase the difficulty of driving the RS into the ground. Even when such RS are buried into the ground, such flanges still do not adequately prevent the RS from pulling up out of the ground. Other means for securing thin RS into the ground also are not adequate.
U.S. Pat. No. 3,545,127 discloses mowing strips integrally attached to retaining strips having underground components. With such combinations, it is very difficult to pack firmly with soil that side of the underground RS which is underneath the MS. Failure to pack this side of the underground RS component firmly with soil would leave the MS/RS combination poorly secured to the ground and would leave the MS poorly supported from underneath. To avoid these problems, MS/RS combinations with underground RS components usually are non-integral, requiring attachment of the MS to the RS after the RS is installed into the ground. U.S. Pat. Nos. 2,184,904, 3,495,352 and 4,372,079 disclose such combinations. However, in comparison to an integral mowing strip/retaining strip combination, a two-piece mowing strip/retaining strip combination is far more likely to become separated or disconnected, permitting grass to encroach through the resulting gap.
RS of previous MS/RS combinations are either constructed of inherently rigid materials or are sufficiently thick to severely restrict the vertical flexibility of both the RS and the attached MS. This reduced vertical flexibility causes gaps to occur between the ground and the MS in regions of changing ground slope. The presence of such gaps creates several problems. First, the gaps can make mowing along the mowing strip difficult by requiring a substantial sideways tilt of the lawnmower. Second, the gaps can cause the lawnmower blade to contact the MS. Third, the gaps can prevent the grass adjacent to the MS from being cut evenly.
Segmented MS/RS combinations have all of the problems described above for segmented MS. U.S. Pat. No. 3,777,421 discloses segmented MS/RS combinations constructed of cap members "snapped" onto base plates secured to the ground. Each cap member is an integral combination of a flat horizontal section forming part of the MS and a vertical wall forming part of the RS. However, the MS/RS combination of U.S. Pat. No. 3,777,421 has the following disadvantages.
Landscape edgings of this type are relatively complicated assemblies of base plates and cap members. Adjoining cap members are preferably interlocked by underlapping base plates. If adjoining base plates are not precisely aligned, the tabs in the overlapping cap members will not "snap" into the corresponding slots in the base plates. Precise alignment and overlap of a relatively large number of segments is unnecessarily complicated, time-consuming, and tedious.
Natural forces, such as expansion and contraction of the ground with freeze/thaw cycles, changes in ground moisture content, fire ant activity, and the like, will cause the joints between adjacent cap members to become separated or jammed. Even a slight separation provides an opportunity for grass to grow between cap members and encroach into an area where grass is not wanted. The stress on jammed cap members can pop them off of the base plates. The use of shiplap joints between cap members does not adequately overcome these problems. The relatively large number of joints present in segmented landscape edgings of this type greatly increases the effort required to maintain separated or jammed joints.
Another disadvantage is that landscape edgings of this type do not conform easily to changes in ground slope. This deficiency, which has the undesirable consequences described above, arises from several factors. One factor is that the cap members of these landscape edgings are stated to be constructed of a relatively rigid material such as filled plastic or fibrous concrete. Such rigid materials inherently prevent the landscape edging from conforming easily to changes in ground slope. Another factor is that the ground might dip between the ends of a cap member, and no means are provided for pulling the center of a cap member into a dip.
U.S. Pat. No. 2,842,344 discloses a rigid landscape edging that is a combination of a MS and a flat vertical wall RS. U.S. Pat. No. 3,713,624 discloses a fence guard that is a combination of a MS and a flat vertical wall retaining strip. Rigid MS/flat vertical wall RS combinations have the following disadvantages.
RS must have sufficient mechanical strength to avoid gross deformation by downward or lateral forces. Such strength is particularly critical when RS are used to retain the gravel in gravel walkways because of the tendency of the gravel to shift laterally when it is walked upon. However, flat vertical wall RS that have adequate mechanical strength to withstand this lateral force are not sufficiently flexible to allow a MS/RS combination to conform easily to changes in ground slope.
Other problems associated with providing flat vertical wall RS with adequate mechanical strength depend on the specific means used to provide such strength. For example, a MS/flat vertical wall RS combination could be made to have adequate mechanical strength by constructing it from a relatively rigid material. However, the use of a relatively rigid material has at least two problems other than that of not permitting the RS/MS combination to conform easily to changes in ground slope.
The first problem is that as a lawnmower is rolled onto one end of a relatively rigid MS, the stake securing the other end of the strip often tends to be pulled up out of the ground. MS constructed of a flexible material such as polyethylene or an elastomer do not have this problem.
The second problem is that it is sufficiently difficult to drive stakes through relatively rigid MS to warrant deliberate means for accommodating stakes. The means disclosed in U.S. Pat. Nos. 2,842,344 and 3,713,624 is integral attachment of the stakes to the MS/RS combinations. Integral attachment of the stakes to the MS/RS combination has at least two disadvantages. One is that it is unlikely that the stakes will be attached in the locations where they will be most needed to accommodate the peculiarities (e.g., changes in ground slope) of any given installation site. Another disadvantage is that a series of stakes attached along the length of a rigid MS/RS combination cannot be driven into the ground one at a time. Instead, the stakes must be driven into the ground by a more difficult and more time-consuming iterative process, each iteration of which comprises driving each stake into the ground only a very short distance. This iterative process is similar to that needed to hammer a thin rigid continuous elongated RS into the ground.
Besides having insufficient flexibility to conform easily to changes in ground slope, a rigid flat vertical wall RS cannot be adequately secured to the ground by attachment to a flexible MS. The RS would yield to lateral forces simply by bending the flexible MS near the joint with the RS. Thus both the rigid RS and the flexible MS would have to be secured to the ground directly by separate means. Another problem with the combination of a flexible mowing strip and a rigid flat vertical wall retaining strip is that the manufacture of such a combination would be relatively expensive, would not provide a strong joint between the MS and the RS, and would yield a warped product.
Perhaps the most significant problem with any MS/flat vertical wall RS combination is that the retaining strips of all such combinations buckle or crimp when forced to conform to changes in ground slope, regardless of the flexibility of the material from which the combination is constructed.